Sunan an-Nasa'i 5024
سنن النسائي#5024SahihIt was narrated from Abu Hurairah that :The Messenger of Allah [SAW] said: "Whoever stands (in he voluntary night prayer of) the Ramadan out of faith and in the hope of reward, his previous sins will be forgiven
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
In-book reference: 47:40